I have a story about this very thing.
My old boss was (and still is) a true English gent. I never heard him swear or get even slightly angry.
Now, working as a civil engineer, he was frequently on site, wearing PPE.
On this particular occasion, he attended a site meeting on an active site on the Tyne.
What I have subsequently found out is that safety helmets have a duration. There are two round 'stamps' on the inside which date the manufacture of the helmet and that they have a 'shelf life' due to degradation of the plastic.
Anyway, back on topic, we were discussing this when my boss walked over and announced that 'He had just had his helmet inspected down the quay' resulted in fits of stifled laughter.